docs: update contact info to GitHub Issues and Security Advisory

docs: update privacy policy for User Token

feat: include authed_user in /slack/exchange response

fix: clarify Slack integration as a feature of the extension

chore: remove tsbuildinfo from git tracking

feat: add privacy policy, terms of service, and direct install support

feat: add /slack/init endpoint for session pre-registration

feat: add /slack/exchange endpoint for token exchange

chore: configure KV namespaces and workspace dependencies

feat: initial project setup for OAuth authentication server